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Protractors

Oddities

Finally, a few protractors in the collections do not obviously belong to any general category, including an object that may not be as old as it appears to be and two instruments that were used by Smithsonian entomologists.

This circular brass protractor is graduated by degrees and bears eight sets of markings by fives from 5 to 45. Each 45-degree section is labeled underneath the numbers: M; an inverted V over a cross; G; an X superimposed on a cross; S; O; A; P. These letters and symbols do not correspond to any standard sets of astronomical, astrological, or mathematical symbols. Two crosspieces on the interior of the protractor are marked with the Latin alphabet: ABCDEFGHIKLM; NOPQRSTVXYZG. It is not known what the final G signifies. A scale above the alphabet is divided into four increments per letter. A brass limb is affixed to the center of the protractor. The limb is divided and marked by tens from 10 to 90. Each division is approximately 3/8" wide.

The instrument is decorated with scrolling, fleurs-de-lis, and a flower at the center of the limb that resembles a pansy. The craftsmanship is crude on the whole, with the angle divisions in particular appearing to be drawn free-hand rather than stamped. The instrument also may have been cut by hand from a sheet of brass. If this protractor is authentic, it likely dates to around 1700.

The Smithsonian purchased this instrument in 1959 from a dealer in antiques, Maurice van Geuns (1905–2000) of New York City. Van Geuns grew up in Groningen in the Netherlands. He spent two years in France in the early 1940s and then enlisted in the U.S. Army in 1943 and served five years.

This semicircular brass protractor is divided by single degrees and marked by tens from 10° to 170° in both the clockwise and counterclockwise directions. The degree lines are crude and likely engraved by hand rather than by machine. A rounded notch is at the origin point. There is no maker's mark. The Department of Entomology in the National Museum of Natural History acquired this object in the late 19th century for use in research. Since inexpensive (10–25 cents) machine-divided brass protractors were widely available during this time period, it is not clear why the curators purchased an instrument that was so poorly manufactured. The protractor may have been made closer to the late 18th century.

This device for measuring angles bears some resemblance to a combination of a sector and dividers. Two steel arms are screwed together so that one arm may be squeezed and the tops of the arms may pinch an object. The stationary arm is split so that the tension on the arms may be adjusted at the screw. The stationary arm is fastened to a brass piece that is divided by single degrees and marked by tens from 0° to 100°. When the other arm is squeezed, it points to a measurement on the brass piece.

An owner's signature on the back of the brass piece appears to read, in script, "bgulp." The letters may be Cyrillic or German. A maker's mark is stamped on the back of the stationary arm: KOCH & Co. The firm to which this maker's mark refers is not known. The Department of Entomology in the National Museum of Natural History acquired this object in the late 19th century for use in research. The object is rusted and tarnished.